In this final part of the series, we cover measuring your physical fitness levels.

There is no single measure of physical fitness, but measures of body composition, aerobic fitness, flexibility and muscular strength and endurance will together provide a picture of overall fitness.

Quick check: Simple ways to evaluate your health

Are you comfortable with your weight? Has it changed for the better or worse in the last 12 months?

Do the pants you bought last year still fit?

Do you get 'puffed' walking up a hill or climbing stairs?

How are you feeling? Energetic and full of life; tired and run down; or somewhere in between.

How often you are unwell? Does it seem to be more than other people?

Body composition

This refers to the relative amounts of fat, muscle, bone and other tissues in your body.

You can't really measure this yourself, although you may have a pretty good idea whether carrying more or less fat on your body over time.

Gyms have two main ways of measuring (actually, making good estimates of) body composition, which can then be compared to norms for different groups of people.

Skinfold test: A trained person uses callipers to grip and measure the thickness of your skin and fat at specified points on your body. The 'sum of skinfolds' measure is used to monitor and compare body fat levels.

Bioimpedance analysis (BIA): An electric current (which you don't feel) is passed through your body and a calculation is made about your percentage of body fat and lean muscle based on the different electrical properties of these tissues.

Aerobic fitness

This describes your heart and lungs' ability to supply oxygen to the working muscles during sustained exercise.

We improve aerobic fitness by exercising at levels that keep the heart rate elevated for a period of time. Brisk walking, swimming, cycling or jogging will all do this.

The simplest way to test your aerobic capacity is to do some aerobic exercise – like running up a hill or walking up some stairs – and see how it feels (it really can be that simple).

You can then compare it to your previous experience of that exercise.

Or even better, do it again in a few months, after you've been regularly exercising, and feel the improvement.

If you want something more technical you'll need to head to a gym for fitness testing.

V02 max: This is a measurement of your maximum oxygen uptake or usage. Testing usually involves a graded exercise test on a treadmill or stationary bike. You breathe into an apparatus so your exhaled air can be measured as the exercise intensity is progressively increased. While V02 max is the most widely accepted measure of aerobic fitness, there are similar tests that don't need to take you to your maximum capacity.

'Beep' test: In this test a course is marked out for you to run. The idea is to arrive at the next marker as the 'bleep' sounds. The trick is that the time between the 'bleeps' becomes shorter over time, so you have to keep running faster. It's designed so that most people can't actually make it to the end, and it's about what level you can reach. This can be compared to other people, or to your own previous test.

Flexibility

Flexibility is about the range of motion you have in your joints.

Generally this is only tested when you have a specific problem in a joint (for example your physiotherapist may test the range of movement in a joint like your wrist, shoulder or knee to identify a problem with the muscles or tendons).

Using and moving your body will keep those joints nimble. To increase your flexibility try stretching exercises, yoga or pilates.

Muscular strength and endurance

Strength is about the force or tension your muscles can exert against a resistance, and muscle endurance is about exerting that force repeatedly without fatigue.

There is a whole raft of tests that can be done for specific muscle groups, but sit-ups and press-ups are probably the most commonly used and you can easily do them at home.

A gym will be able to compare your performance to others of the same gender and age group, but you can test yourself against previous performance by keeping a record of either how many you can do in total, or within a certain time period.

Sit-ups: A good test of strength and endurance of the abdominals and hip-flexor muscles. The average number of sit-ups a woman between 36-45 years old can do in one minute is 20-22; for a man it's 28-29.

Press-ups: Test the strength endurance of chest, shoulder and tricep muscles. Women should choose the knees on the floor version. An average 40-49 year old woman should be able to do 11-14; a man of the same age 13-16.

Why fitness is important

Some of us treat exercise as though it's optional. It's not: it's essential for our health.

People who are very active in their daily life or who exercise regularly are less likely to develop cardiovascular disease.

In fact, inactive or unfit people have almost twice the risk of dying from coronary heart disease than active people.

They also have a much higher risk of developing type 2 diabetes.

Being active helps prevent, and can help the treatment of, high blood pressure, high cholesterol and impaired glucose tolerance. Physical activity also reduces your overall risk of developing any type of cancer. There is little doubt that it is protective against colon cancer and it is also strongly associated with reduced risk of breast cancer in post-menopausal women.

And of course, being active improves strength and endurance, joint mobility, as well as helping control the amount of fat your body is storing.

Along with the all the physical health benefits of moving your body, your mental health will benefit too. Physical activity lifts your mood, reduces feelings of stress and anxiety and also helps you sleep.

There are a number of studies showing that physical activity helps improve people's self-esteem, and exercise has even be used to treat clinical depression and can be just as effective as psychotherapy or medications.

When we talk about getting your 30 minutes (or more) of exercise each day, it might be helpful to remember that this doesn't have to be in one session. It has been shown that three 10-minute bouts of activity are just as effective, as long as you're using as much energy overall.

In terms of how intense your exercise needs to be, it seems that for heart health and mental health it doesn't have to be really strenuous exercise to give you benefits; a brisk walk will do the trick. However, for the best protection against cancer it seems moderate or vigorous activity is needed to give a significant protective effect.

Remember that it's never too late to start exercising. Even if you have been inactive most of your life, improving your fitness now can have a big impact.

And if you can't bear the thought of getting into track shoes and shorts just yet, then don't. But you can still increase your 'incidental activity':

Walk to the dairy rather than taking the car.

Use stairs rather than a lift, even if you have to start with walking only part of the way.

At the supermarket or mall park further away from the entrance.

Go for a walk around the block at lunchtime.

Clean the house

Would the army have you?

For a life in the army you need to be fit – but how fit do you have to be just to be accepted for recruit training? For the 'entry fitness level' you will need to be able to do the following:Men: Run 2.4km in 12 minutes or less; 45 sit-ups; 15 press-ups.Women: Run 2.4km in 14 minutes or less; 35 sit-ups; 8 press-ups. And the required fitness level once you've graduated is tougher.

Don't forget about nutrition

Are we in denial? A recent survey of 12,000 people in the US found that the majority of people who are obese or even morbidly obese will tell you they eat a healthy diet. These people are either in denial, or the really don't know what a healthy diet looks like.

Eating a balanced diet that provides all the nutrients you need is obviously vital to good health. And you can enhance your health by getting more than just the 'basics' in terms of nutrients.

Fruits and vegetables, for example, are choc full of an enormous range phytonutrients that seem to enhance our health in ways we don't yet understand.

Even though the general guidelines encourage us to eat 5+ a day of fruit and vegetables, for some reason we often forget about the 'plus' and congratulate ourselves when we get to 5. Most of us know by now we need to limit our intake of saturated fats, but a small amount of unsaturated fats is really good for us.

And we need to take care about the amount of sodium in our diets. This seems to be especially important for people who are overweight or obese, or show any other risk factors for cardiovascular disease or type 2 diabetes.

A balanced diet for a healthy adult includes:

6+ serves of breads and cereals each day: providing fibre, vitamins and minerals; aim for more whole grain and less refined breads and cereals for more fibre and nutrients.

5+ serves of fruits and vegetables every day: providing low-fat vitamins, minerals and fibre; go for a wide colour range.

At least 1 or more serves of protein foods like meats and poultry, seafood, eggs, legumes and pulses, nuts and seeds: always trim fat from meats and use low-fat cooking methods; aim for a variety of foods in your diet.

Don't overdo the amount of fats and oils, sugary foods, salt and alcohol: a little is good but more is not better.

Ensure you're getting plenty of low-or no-kilojoule fluids during the day as well.

The bottom line

Looking after ourselves so that we can be healthier in 10 or 20 or 30 years' time is not always terribly inspiring.

The good thing about all of the measures we've talked about is that not only will they indicate how we're going for the long-term, they'll also be a good indicator of how things are right now.

It's not a case of one single measurement being the 'best' or the only one to worry about. It's more a case of the combination of all of them.

Chances are if you score well on all of those tests you'll be one of those people who have a good immune system, high energy levels and the resulting positive outlook.

Unless you have a specific condition, you won't be the person who's sluggish by lunch-time, catching every cold that's going and suffering from bloating or indigestion on a regular basis.

There are many things you can't control in life. We're all going to get older. Some people have the advantage of their genes, some the disadvantage.

But we can do the very best we can with the cards we've been given – we can aim to be the best we can be at any age or stage of our lives.

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